Argument matcher `check` called twice when the mocked method was only called once.

[roy-t]

When I was writing a test that required a more complex argument matcher I resorted to using check. To my surprise check is evaluated twice when the mocked method was only called once. I believe this is a bug as I think it is reasonable to assume that if a method is called once the argument matchers for each argument of that method are also only called once. Otherwise you might run into problems (as I did) if the arguments can change state.

I managed to get the reproduction down to this, but I did not get much wiser from the stack trace or mockito-kotlin source code to get any further insights.

import org.junit.jupiter.api.Test
import org.mockito.kotlin.check
import org.mockito.kotlin.mock
import org.mockito.kotlin.times
import org.mockito.kotlin.verify
import java.util.concurrent.atomic.AtomicInteger
 
class Tests {       
    @Test
    fun testCase() {
        // Create something that we can mock, note counter is not touched
        class Foo {
            fun bar(counter: AtomicInteger) {}
        }

        // Create the mock, again the counter is not touched
        val mocked =
            mock<Foo> {
            }

        val counter = AtomicInteger(0)

        // Call bar exactly once, verify that the counter is still untouched
        mocked.bar(counter)
        assertThat(counter.get()).isEqualTo(0)

        // Verify that bar was indeed called exactly once  
        verify(mocked, times(1))
            .bar(
                // Check how many times the argument matcher runs, by increment the counter each time
                check { it.incrementAndGet() },
            )

        // We would expect counter to now be 1, but it is actually 2, so this assert fails.
        assertThat(counter.get()).isEqualTo(1)
    }
 }

I'm using the following dependencies:

• mockito-kotlin 5.4.0
• junit 5.10.3

[tschut]

I think this is caused by Times::verify, which first checks if there are any invocations at all before checking the number of invocations:

    @Override
    public void verify(VerificationData data) {
        List<Invocation> invocations = data.getAllInvocations();
        MatchableInvocation wanted = data.getTarget();

        if (wantedCount > 0) {
            checkMissingInvocation(data.getAllInvocations(), data.getTarget());
        }
        checkNumberOfInvocations(invocations, wanted, wantedCount);
    }